1. Field of the Invention
The present invention relates to a tape carrier package (TCP) which is a thin semiconductor device, a fabrication method thereof, and a tape carrier.
2. Description of the Related Art
A conventional IC packaging is used for protecting an IC body from external substances and mounting on a circuit board. In recent years, because IC products have an even wider range of applications, and material, size and configuration of packages have become diversified, and as the demand to mount a larger number of pins at an even higher density has increased, the demand to add higher values to the package itself has increased even more.
One such package configuration is a TOP (tape carrier package). A tape carrier herein is a semiconductor device fabricated in the following manner. A device hole is first formed in a flexible base tape, leads (wiring patterns) are formed by, for example, photolithography, and then a solder resist is formed to protect the leads. The TOP is a package in which semiconductor elements are mounted on the tape carrier and sealed by, for example, a resin. A package in which semiconductor element(s) are mounted on a tape carrier but are not sealed by a molding is referred to as a structure.
In a conventional tape carrier, on a photographic film-like base tape made of, for example, polyimide, device holes are formed along the longitudinal direction of the base tape. Many sprocket holes are provided in the vicinity of and along the both width direction edges of the base tape so as to be parallel to the device holes, to facilitate conveyance of the base tape during manufacturing thereof, or the like. A plurality of leads is formed as inner lead portions which protrude toward each device hole. These leads are generally formed of a conductive metal, such as aluminum, copper, or the like. A solder resist is formed on the leads to protect the wiring pattern at a portion of the leads that are on the base tape. The entire surface of each of the leads is plated with Sn (tin), Au (gold), solder, or the like for protection and for bonding the leads.
To mount semiconductor elements on the tape carrier, the semiconductor elements are bonded to the inner lead portions by, for example, eutectic reaction or thermo-compression. Then, a mold is formed by a resin, or the like. Finally, the base tape is cut out to form each package. The package is surface mounted on, for example, a printed wiring board by bonding outer lead portions thereof to the printed wiring board.
A conventional TCP is shown in FIGS. 15A and 15B. FIG. 15A is a plan view of the conventional TCP and FIG. 15B is a sectional view of the conventional TCP taken along line C-Cxe2x80x2 of FIG. 15A. A base film 101 is made of, for example, polyimide. Sprocket holes 102 are formed on the base film 101 for conveyance of the base film 101. A semiconductor element 110 includes protruding electrodes 111 which are connected to terminals 103 via inner lead portions 105. The terminals 103 are connected to external circuits. The inner lead portions 105 and the terminals 103 are made of copper, formed by etching and plated with Sn, Au, or solder. The terminals 103 are wider than the inner lead portions 105. A solder resist 106 is formed on the inner lead portions 105 to protect the copper-made pattern except the terminals 103. A sealing resin 112 is provided to cover and protect the semiconductor element 110 and the inner lead portions 105.
Another conventional TCP is shown in FIGS. 16A and 16B, which is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-21703. FIG. 16A is a plan view of an IC package and FIG. 16B is a sectional view taken along line C-Cxe2x80x2 of FIG. 16A. This TCP is fabricated in the following manner. Device holes 104 are formed on a tape base 102. Leads 108 are provided on the tape base 102 at the periphery of the device hole 104. Several semiconductor chips 106 are stacked in the device hole 104. Tips of the leads 108 are formed as inner lead portions 108a, which are connected to bumps 110 disposed on the semiconductor chips 106. Then, the semiconductor chips 106 and the device hole 14 are sealed by, for example, a sealing resin 112. This conventional structure has drawbacks in that, because the semiconductor chips 106 are stacked with chip surfaces on which leads 108 are to be bonded facing each other, it is necessary to overturn the package during bonding of the leads 108. Further, because only the leads extending in opposed two directions are connected to each semiconductor chip 106, there are limits to increasing packaging density of semiconductor chips.
For several years, an IC package, known as a BGA (i.e., ball grid array) package which can be mounted at a high density on a printed wiring board, has been developed. In the BGA package, metal balls for connecting to external circuits are disposed in a grid-like pattern at the bottom of the IC package. In this configuration, because terminals for external connection are disposed in a two-dimensional plane, the number of pins can be increased without changing the dimensions of the package very much.
FIGS. 17A and 17B illustrate a BGA structure disclosed in JP-A No. 8-148526, which uses a tape carrier. FIG. 17A is a sectional elevation view, and FIG. 17B is a bottom view, of a BGA type IC package. The BGA semiconductor device has excellent moisture resistance property, and can be fabricated at a low cost, and can be produced in large quantities. In the BGA semiconductor device, a device hole 102a is formed in the center of a flexible resin substrate made of, for example, polyimide film. Leads 103 formed of a copper foil are provided at a surface of the substrate, and the substrate is used as a TCP substrate. Tips of the leads 103 are formed as inner lead portions 103a, which are connected to electrodes 101a of a semiconductor chip 101. Each lead 103 is connected to a corresponding bump 105, such as a solder ball disposed at the bottom surface of the package.
In such conventional tape carriers, only one semiconductor element can be mounted on a single tape carrier, and it is difficult to mount several semiconductor elements, particularly semiconductor elements having different sizes, on a single tape carrier at a high density to improve functions of the semiconductor package.
In the package configuration which employs a combination of the tape carrier and the BGA, a larger number of external terminals may be extended from a package of the same size as those of conventional ones. However, it is very difficult to improve functions of the package itself by densely mounting several semiconductor elements on a single tape carrier.
In view of the aforementioned, an object of the present invention is to improve functions of and to add further values to a semiconductor package by mounting several semiconductor elements (particularly semiconductor elements of different sizes) in a single device hole of a tape carrier without losing TCP advantages of being compact and thin.
A semiconductor package of the present invention comprises: a tape carrier; a first semiconductor element having a surface and a first electrode, on which surface the first electrode is provided; a longer lead which is provided on the tape carrier and connected to the first electrode; a second semiconductor element having a surface and a second electrode, on which surface the second electrode is provided, and the first semiconductor element is stacked; a shorter lead which is provided on the tape carrier and connected to the second electrode and is shorter than the longer lead; and a resin material which seals the first semiconductor element, the second semiconductor element, the longer lead and the shorter lead.
In this structure, two semiconductor elements can be stacked and accommodated in a single TCP and the semiconductor device can be made thinner. Therefore, functions of the TCP can be improved and higher values can be added to the TCP.
Another semiconductor package comprises: a tape carrier; a first semiconductor element having a surface and a first electrode, on which surface the first electrode is provided; a longer lead having two ends and a first land, the one end being connected to the first electrode and the other end forming the first land on the tape carrier; a second semiconductor element having a surface and a second electrode, on which surface the second electrode is provided, and the first semiconductor element is stacked; a shorter lead having two ends and a second land, the one end being connected to the second electrode and the other end forming a second land on the tape carrier; a resin material which seals the first semiconductor element, the second semiconductor element, the longer lead and the shorter lead; and solder balls, which are mounted on the first and second lands for external connection.
In this structure, since the TCP employs the BGA structure, the TCP can be solder-mounted on a circuit board with other parts at the same time by reflowing solder.
The present invention further includes at least another longer lead and at least another shorter lead, wherein each of the longer leads and each of the shorter leads are arranged so as to alternate with each other.
In this structure, because a plurality of first and second electrodes and a plurality of longer and shorter leads are provided, and each of the longer leads and each of the shorter leads are arranged alternately adjacent to each other, the upper and the lower semiconductor elements can be easily connected.
The second semiconductor element is larger than the first semiconductor element, and comprises a surface area that faces the first semiconductor element and the second electrode is disposed outside the area.
The first semiconductor element includes a first surface, on which the first electrode is formed, and a second surface, which is opposite the first surface; the second semiconductor element includes a third surface, on which the second electrode is formed, and a fourth surface, which is opposite the third surface; and the first semiconductor element and the second semiconductor element are stacked such that the second surface faces the third surface.
In this structure, the lower semiconductor element is larger than the upper semiconductor element, and the electrode of the lower semiconductor element is disposed outside the area overlapping the upper semiconductor element. Therefore, the upper and the lower semiconductor elements can be stacked such that the surfaces having the electrodes thereon face the same direction. Accordingly, it is unnecessary to overturn the package during bonding of the inner lead portions to the electrodes as in the case of conventional package.
Further, the fourth surface is substantially devoid of the resin material, and the resin material is applied to substantially the remainder of the package.
Accordingly, since no resin material is applied to the bottom surface of the lower semiconductor element, the package on the whole can be thinner.
The first and the second semiconductor elements are adhered to each other.
In this structure, each of the lower and the upper semiconductor elements has two sets of edges which are substantially parallel to each other, and each of the longer and the shorter leads extends orthogonally to each edge. Accordingly, the leads are arranged regularly and the TCP can be made compact.
The longer and the shorter leads extend outwardly in the substantially same plane. The first and the second semiconductor elements are bonded together using an adhesive.
Such a structure makes it easy to mount the TCP on the circuit board.
Further, to overcome the disadvantages of the prior art, a tape carrier of the present invention includes: a base tape having a device hole formed therein; and a plurality of leads provided on the base tape, wherein inner lead portions of the leads which extend from the periphery of the device hole toward the center of the device hole have several different lengths.
In this structure, several semiconductor elements of different sizes can be mounted in a single device hole of the tape carrier. Therefore, functions of the TCP can be improved and higher values can be added to the TCP without losing TCP advantages of being compact and thin.
Further, in the present invention, surfaces of several semiconductor elements are spaced apart from one another. Therefore, mutual interference between one semiconductor element and other semiconductor elements resulting from noise, or the like, generated by the other semiconductor elements can be reduced. Accordingly, improper operations of the semiconductor elements can be prevented while achieving aforementioned objects.
In the present invention, because BGA is employed at the external connection terminals of the outer lead portion, the arrangement of the leads can be determined freely. Therefore, the number of degrees of freedom in the arranging of the terminals which output signals of the mounted semiconductor element and designing of the device using the TCP increases. Accordingly, the synergy between the TCP and the BGA helps to improve functions of the TCP, to integrate an increased number of chips, and to add higher values to the TCP in the same mounting area, without losing the TCP advantages of being compact and thin. By stacking several TCPs of BGA type, output and input terminals of two or more tape carriers can be connected to a mount substrate in a mount area of a single tape carrier. Moreover, because semiconductor elements mounted on a tape carrier can be connected to one another, semiconductor elements can be integrated even more densely and the functions of the TCP can be further improved.